#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
	double a = 1;
	double n = 1;
	for (n = 1; n < 1000000; n++)
	{
		a *= (2 * n * 2 * n) / ((2.0 * n - 1) * (2.0 * n + 1));
	}
	printf("%lf", 2 * a);
	return 0;
}
